Heat seeking or infrared (IR) missiles have become a major threat against military vehicles and aircraft when employed by enemy forces as well as against civilian vehicles and aircraft by guerilla groups and other insurgents. Jamming waveform programs have been derived from a priori data on missile threat characteristics and from experiments to jam such IR missiles. However, one of the problems is that all of the known heat seeking missiles are not jammed by the same program. Presently available IR jammers consists of a source of infrared radiation and some means to modulate the radiation emitted by the source to produce a desired jamming signal. If multiple jamming programs are required to protect against multiple missile threats the planes or vehicles to be protected would generally have to have multiple jammers associated therewith. In addition to being expensive, multiple jammers can present a problem in that one missile could use a jammer for another missile as a beacon.
This problem has been somewhat alleviated by the system disclosed in U.S. patent application Ser. No. 373, 237 filed on Jun. 25, 1973 for xe2x80x9cMultiple Spectral Band Opto-Mechanical Modulatorxe2x80x9d and assigned to assignee of the present application. This application discloses modulators for an infrared source to provide two distinct jamming programs from a single source, One modulator described in this patent application comprises a first rotating filter wheel having alternating radial segments of transparent and short wavepass filter material, a second rotating filter wheel having alternating radial segments of transparent and long wavepass filter material and a stationary wheel having alternating transparent and opaque radial segments positioned intermediate the first and second rotating wheels. This system provides simultaneous but independently radiation in two distinct spectral regions at different pulse repetition frequencies, if desired. This system is good in providing modulation of an IR source to countermeasure two missiles requiring different countermeasure programs. However, it is limited to two such programs.
Accordingly, it is an object of this invention to provide a new and novel modulator.
It is another object of this invention to provide a modulator which enables a single IR source to jam any number of different type missiles which are nearly mutually exclusive spectrally.
It is a further object of this invention to provide a modulator for generating different carrier and spin pulse repetition frequencies, pulse widths, pulse shapes, pulse repetition frequency sweep ranges and pulse repetition frequency sweep rates for different missile types simultaneously and with negligible interference.
It is yet another object of this invention to provide a system for simultaneously jamming a number of missiles.
Briefly, simultaneous jamming of a number of missile types which are nearly mutually exclusive spectrally are jammed with a single IR source by chopping or spatially modulating the output from the IR source with a series arrangement of spectral band-reject filters. Each missile to be jammed requires a distinct modulating reticle comprising alternating segments which alternately pass radiation at all wavelengths of interest and block or reject radiation at the wavelength of the missile to be jammed. For spin scan missiles these latter segments are further divided into segments which alternately pass all wavelengths of interest and block or reject radiation at the wavelengths of the missile to be jammed. This latter division of the segments provides carrier frequency. The band-reject segment may be either reflective or absorptive.